Intralobar Pulmonary Sequestration with Rete Mirabile As Part of Its Systemic Artery

Open Journal of Medical Imaging, 2020, 10, 89-95 https://www.scirp.org/journal/ojmi ISSN Online: 2164-2796 ISSN Print: 2164-2788 Intralobar Pulmonary Sequestration with Rete Mirabile as Part of Its Systemic Artery Patrick Mailleux1, Marylène Clausse2 1Department of Imaging, Clinique St Luc, Bouge, Belgium 2Department of Oncology, Internal Medicine, Clinique St Luc, Bouge, Belgium How to cite this paper: Mailleux, P. and Abstract Clausse, M. (2020) Intralobar Pulmonary Sequestration with Rete Mirabile as Part of Intralobar sequestration (ILS) is a complex lung lesion where part of a lower Its Systemic Artery. Open Journal of Medi- lobe lacks communication with the tracheobronchial tree and receives an ab- cal Imaging, 10, 89-95. errant arterial blood supply from the systemic circulation. That systemic ar- https://doi.org/10.4236/ojmi.2020.102008 tery is usually large, originating from the thoracic aorta or the abdominal Received: April 29, 2020 aorta and its upper branches. We describe a case of ILS where a large systemic Accepted: May 16, 2020 artery coming up from below the diaphragm is formed by the convergence of Published: May 19, 2020 many very small serpiginous arteries coming up from the area of the celiac Copyright © 2020 by author(s) and trunk and common hepatic artery: a kind of “rete mirabile”. This peculiar Scientific Research Publishing Inc. morphology was not described before. This work is licensed under the Creative Commons Attribution International Keywords License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ CT, Aberrant Systemic Artery, Congenital Anomalous Artery, Pulmonary Open Access Sequestration, Rete Mirabile 1. Introduction Pulmonary sequestration is a congenital pathology where part of the lung, usually in the lower lobes, has no connection with the central airways, and an arterial supply coming from a systemic origin. It is called an intra-lobar sequestration (ILS) when the abnormal lung segment lies in the same pleural sac, while it is an extra-lobar sequestration (ELS) when exists a separate pleural cavity. The large feeding artery having a systemic origin is often the clue to the diagnosis. In the patient, a very peculiar finding is the appearance of the abnormal systemic artery, which is formed by the confluence of a meshwork of tiny arteries coming up from the area of the celiac trunk. DOI: 10.4236/ojmi.2020.102008 May 19, 2020 89 Open Journal of Medical Imaging P. Mailleux, M. Clausse 2. Case Report A 62-year-old female patient presented with rectorrhagia. A colonoscopy was found a sigmoid colic tumor later confirmed by CT (Figure 1) and surgery to be T3N0, with no liver ou lung metastasis. The patient had a 60 year/pack smoking history, but no specific complaints of chronic bronchitis. Chest CT made in the extension work-up showed complex alterations in the posterior basal segment of the right lower lobe (Figure 2(A)) just above the diaphragm while a 18F-FDG PET/CT scanner made for the colic tumor showed no uptake in the lung right lower lobe condensation (Figure 2(B) and Figure 2(C)). Thin slices oblique reconstructions of Figure 3 demonstrate that there is some collapsed lung parenchyma around small tubular bronchiestasis that have a completely different orientation than the normal bronchial tree (Figure 3(B) and Figure 3(D)). They are roughly horizontal, parallel to the diaphragm, not connected to the normal bronchial tree and have a different orientation. Adja- cent and medial to it, a 6.5 mm wide large systemic artery with an ante- rior-posterior direction, coming up from below the diaphragm through a defect between the main right diaphragmatic pillar (star) and the right accessory pillar. Contrary to all ILS described in the literature, the proximal part of that large systemic artery is not as large and regular than its distal intra-pulmonary part: it seems to be formed by the convergence of many very small serpiginous arteries coming up from the area of the celiac trunc and the common hepatic artery. So there is a “rete mirabile” (RM) composed of many small arteries converging up through a small hiatus in the diaphragm to reunite into one large systemic trunk of the right ILS (Figure 4(C), Figure 4(D), Figure 5(A) and Figure 5(D)). There were no pulmonary symptoms related to the ILS (no dyspea, coughing, hemoptysis), so that no treatment was proposed for the ILS. The colic tumor was resected, the staging was pT3N0M0 on the basis of the histological findings, the absence of invasion of the 14 resected lymph nodes and the otherwise normal 18F-FDG PET. No chemotherapy was given as there were at this time no high risk factor of recurrence. Figure 1. 1(A) Axial CT slice, with intra-rectal contrast (star). 1(B) Sagittal reconstruction. The distal sigmoid colon tumor is shown by the thin arrows and the curved arrow indicates tumor effraction through the serosa, it proved to be a T3N0M0 tumor. DOI: 10.4236/ojmi.2020.102008 90 Open Journal of Medical Imaging P. Mailleux, M. Clausse Figure 2. 2(A) axial CT through the right posterior-basal lung segment. 2(B) and 2(C) are 18F-FDG PET/CT axial and coronal images through the same region. The lung postero-basal lesion (star) has irregular bor- ders, On 2(B) and 2(C), there is no significative 18F-FDG uptake. Figure 3. CT axial slices, at the level of the lung condensation (3(A), 3(B) and 3(C)), 3(D) sagittal reconstruction. The bronchi (thin arrows) inside the lesion above the diaphragm are irregular and dilated, they have a very different orientation than the proximal bronchi (curved arrow). On 3(C) and 3(D) is the very large systemic artery (arrowheads). Figure 4. Abdominal CT Axial slices from the ILS 4(A) above to the celiac trunk below (black arrowhead in 4(F). A series of very small arteries arising from the celiac area (thin arrows) converge to reunite into the large systemic artery (curved arrow) of the ILS. They pass through a gap in the diaphragm on the right side of its right pillar (star in 4(B) and 4(C)). DOI: 10.4236/ojmi.2020.102008 91 Open Journal of Medical Imaging P. Mailleux, M. Clausse Figure 5. 5(A) is a MIP oblique sagittal reconstruction above the common hepatic artery (black arrow), showing the thin trabeculated arteries (thin arrows) going up from the region of the celiac trunc and hepatic artery to merge into the large systemic vessel (large arrowheads) which enters the ILS. 5(B) is a Volume Reconstruction from the angio CT. Hepatic artery (white curved arrow), splenic arteric (black curved arrow), rete mirabile (thin white arrows), large systemic vessel of the ILS (large arrowheads). Two years later, a liver metastasis was detected in segment 2 and treated by left hepatectomy followed by FOLFOX chemotherapy for 6 months. Five years later two new liver metastases were found in segment 8. The patient received 3 cycles of FOLFOX associated with PANitumumab followed by 1 cycle of PANi- tumumab alone which achieved partial response on the liver lesions that were resected with R0 margins. Since that last surgery, the patient receives adjuvant TOMOX chemotherapy (Raltitrexed plus oxaliplatin without 5FU) at a 20% re- duced dosage and one year later, MRI and CT exams do not show any no recurrence. During those 8 years, the ILS of the right pulmonary lobe did not change and the patient presented no specific symptoms that could be related to it. 3. Discussion Pulmonary sequestration (PS) is a rare congenital malformation that accounts for 0.15% - 6.4% of all pulmonary malformations [1]. In the year 1946, Pryce was the first to discribe the entity [2], which is an area of non-functioning broncho- pulmonary tissue that is separated from the tracheobronchial tree and receives its arterial blood supply from the systemic circulation. The aberrant systemic arterial supply may involve a single or multiple vessels, and the latter accounts for 15% - 20% of pulmonary sequestration [1]. By definition, there is no communication of the lesion with the tracheobronchial tree. Pulmonary sequestration can be divided into two distinct groups based on the relationship of the aberrant segmental lung tissue to the pleura: the intralobar sequestration (ILS) which accounts for the majority (75% - 85%) of all sequestrations and present later in childhood with recurrent infections [2]. ILS is closely connected to the adjacent normal lung and does not have a separate pleura while the less common extralobar sequestration (ELS) is separated from any surrounding lung by its own pleura. ELS usually is present in the neonatal period with respiratory distress, cyanosis, or infection, with a recognized male DOI: 10.4236/ojmi.2020.102008 92 Open Journal of Medical Imaging P. Mailleux, M. Clausse predilection, and infradiaphragmatic location in 10% of cases [3]. The most accepted theory concerning its pathogenesis suggests that PS is the result of an insult to the tip of developing lung buds. In early developing stages, the tips of the dividing bronchial buds are supplied by systemic capillary plexus derived from the primitive aorta. This plexus regresses with further lung matu- ration as the developing pulmonary artery takes over [4]. If an insult to the developing lung buds occurs, the original vessels derived from the aorta keep ex- isting and that explains the presence of the systemic feeding vessel of the PS. Imaging studies for the investigation of a suspected case of pulmonary sequestration have two principal objectives: to rule out other pathologies and to confirm the presence of an anomalous arterial supply.

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